Diabetics, especially those being treated with insulin, have a significantly greater risk of developing cardiac failure than do normal individuals. Previous studies have suggested that the sugar transport system of hearts from diabetic animals did not respond to higher work loads or to insulin as well as normals. The goal of this project is to characterize the sugar transport system in isolated, perfused hearts of normal and diabetic animals performing at various levels of ventricular pressure development, to examine the hypothesis that 1) a defect in transport exists in diabetic heart which prevents stimulation of the transport process by increasing work loads, and 2) a sufficiently fast rate of sugar entry is necessary for recovery of myocardium from increased work loads. Characterization of transport will involve measurement of the kinetics of non-metabolized sugar movement. Sensitivity of diabetic hearts to insulin will be investigated by measuring transport rates in working hearts given insulin, by study of relationships between cardiac fatty acid and triglyceride content and insulin sensitivity and by measurement of insulin binding to isolated beating myocytes. Hearts will also be analyzed to determine the effect of glucose transport rates on generation of sufficient ATP and creatinine phosphate to allow diabetic hearts to work normally and recover from periods of increased ventricular pressure development.